x86: add periodic corruption check

Perodically check for corruption in low phusical memory.  Don't bother
checking at fault time, since it won't show anything useful.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/setup.c

@@ -623,6 +623,7 @@ static void __init setup_bios_corruption_check(void)
 }
 
 static int __read_mostly bios_corruption_check = 1;
+static struct timer_list periodic_check_timer;
 
 void check_for_bios_corruption(void)
 {
@@ -650,6 +651,22 @@ void check_for_bios_corruption(void)
 		dump_stack();
 }
 
+static void periodic_check_for_corruption(unsigned long data)
+{
+	check_for_bios_corruption();
+	mod_timer(&periodic_check_timer, jiffies + 60*HZ);
+}
+
+void start_periodic_check_for_corruption(void)
+{
+	if (!bios_corruption_check)
+		return;
+
+	init_timer(&periodic_check_timer);
+	periodic_check_timer.function = &periodic_check_for_corruption;
+	periodic_check_for_corruption(0);
+}
+
 static int set_bios_corruption_check(char *arg)
 {
 	char *end;

arch/x86/mm/fault.c

@@ -848,8 +848,6 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
  * Oops. The kernel tried to access some bad page. We'll have to
  * terminate things with extreme prejudice.
  */
-	check_for_bios_corruption();
-
 #ifdef CONFIG_X86_32
 	bust_spinlocks(1);
 #else

arch/x86/mm/init_32.c

@@ -907,6 +907,8 @@ void __init mem_init(void)
 	int codesize, reservedpages, datasize, initsize;
 	int tmp;
 
+	start_periodic_check_for_corruption();
+
 #ifdef CONFIG_FLATMEM
 	BUG_ON(!mem_map);
 #endif

arch/x86/mm/init_64.c

@@ -769,6 +769,8 @@ void __init mem_init(void)
 {
 	long codesize, reservedpages, datasize, initsize;
 
+	start_periodic_check_for_corruption();
+
 	pci_iommu_alloc();
 
 	/* clear_bss() already clear the empty_zero_page */

include/linux/kernel.h

@@ -246,6 +246,7 @@ extern int root_mountflags;
  * able to scatter it around anywhere in the kernel.
  */
 void check_for_bios_corruption(void);
+void start_periodic_check_for_corruption(void);
 #else
 static inline void check_for_bios_corruption(void)
 {